1. Field of the Invention
The present invention relates to a gas sensor system and a method for controlling a gas sensor.
2. Description of the Related Art
Hitherto, a gas sensor has been used for detection of specific gas components contained in the exhaust gas or the like of an internal combustion engine, or for measurement of the concentration of specific gas components. As such a gas sensor, a sensor is known that uses a reference cell and a detection cell, each having a zirconia solid electrolyte. In this sensor, the current flowing through the detection cell is controlled so that an electromotive force of the reference cell becomes constant. In this regard, a technique is known for controlling the current in a time-division manner.
[Patent Document 1]
    Japanese Unexamined Patent Application Publication No. H10-300720-A
3. Problems to be Solved by the Invention:
When a gas sensor system is used for engine control, a control (for example, air-fuel ratio control) using a sensor output is desirably started as soon as possible after starting the engine in order to improve the accuracy of the engine control. On the other hand, when a sensor is used in which sensor elements are heated to a target temperature by a heater, it takes some time until the temperature of the sensor elements achieve the target temperature from the initial time of heating. In this case, the frequency characteristics of the gas sensor will change depending on the temperature of the sensor elements. However, sufficient studies have not yet been conducted with regard to control of the gas sensor in consideration of the temperature dependence of the frequency characteristics.